Exciton-exciton annihilation and exciton kinetics in poly(di-n-hexylsilane)

Abstract

We have found that charge carriers can be generated by exciton-exciton annihilation in solid films of poly(di-n-hexylsilane). We use this phenomenon to study the kinetics of excitons at ambient temperature and show that the rate constant for exciton-exciton annihilation γ is 2×${10}^{\mathrm{-}7}$ ${\mathrm{cm}}^3$ ${\mathrm{s}}^{\mathrm{-}1}$, in excellent agreement with the value we obtained previously by other means. The quantum efficiency for carrier production, at an electric field of 2×${10}^5$ V ${\mathrm{cm}}^{\mathrm{-}1}$, is 1.3×${10}^{\mathrm{-}3}$ per annihilation event. We also show that γ is independent of the initial energy of the exciton state, even to energies far out on the long-wavelength tail of the exciton absorption band, and that the excitons remain mobile throughout their 600-ps lifetime.